The present invention relates to the field of emulsified effluent processing, notably petroleum effluents from production wells. The emulsions concerned are those whose disperse phase is electrically conducting, unlike the continuous phase, for example water dispersed in an organic phase such as oil.
It is important to separate the water from the effluent produced so as to limit the size of the processing and transport equipments. After passing the emulsified effluent through conventional water/oil separators, the effluent still contains about 1 to 5% of water emulsified in the oil. The goal of the present invention is to decrease these residual amounts of water and salts in order to meet the technical requirements of the downstream processes.
Document U.S. Pat. No. 5,647,981 describes a device which combines the principle of an electrocoalescer with centrifugation.
Water-in-oil emulsions can be broken by coalescence of the water drops through the action of an electric field. However, in order to increase the efficiency of these electrostatic separators, one tries to increase the electric potential between the electrodes, with a real risk of appearance of breakdown phenomena between electrodes. On the other hand, considering the residence time required between the electrodes, the flow of effluent that can be treated is low, unless an installation of disproportionate size is used.
The present invention overcomes these known drawbacks by optimizing the combination between an electrocoalescer of determined size and centrifugal and separation means specific to said coalescer.
The present invention thus relates to a device for separating an effluent comprising phases of different density and conductivity, the device comprising a pair of electrodes, means for introducing the effluent between said electrodes, means intended for separation and discharge of said separated phases. According to the invention, the separation means comprise at least one centrifugal element including a helical channel in which the effluent is centrifuged after passing between the electrodes.
The helical channel can consist of a helical wall arranged in an annular space.
The helical wall can be in contact with the internal tube but provide a clearance with the wall of the external tube.
The helical channel can consist of a helical tube.
Said electrodes can exhibit the shape of cylinders arranged along the same axis.
The section of flow of the helical channel can be so determined that the velocity of the effluent increases in relation to the velocity of the effluent in the vicinity of said electrodes.
The lighter phase can be discharged through an axial line.
The discharge means can comprise a cyclone and an axial port for discharge of at least part of the centrifuged phase.
The discharge means can comprise at least one port on the periphery of said centrifuged effluent so as to discharge at least part of the centrifuged phase.
The invention also relates to a method of separating an effluent comprising phases of different density and conductivity, comprising at least an electrocoalescence stage between two electrodes, a separation stage, a stage of discharge of said separated phases. According to the method, the separation stage follows the coalescence stage and includes at least a stage of centrifuging the effluent in a helical channel.
The centrifugation stage can be such that the velocity of the effluent is increased in relation to its velocity between said electrodes.
A centrifuged phase discharge stage can follow the centrifugation stage by using a cyclone into which said helical channel opens.
At least part of the centrifuged phase can be discharged through at least one port arranged on the periphery of and downstream from said helical channel.